I'm a little confused about your situation. Are you living overseas now and that is where you adopted the lab, or were you stateside and left for overseas?
When you say registered, do you mean licensed or registered on base as belonging to you? Are you a service person? Most U.S. Posts have a vet on base.
Sounds like the little guy needs to be looked at sooner than the 24th if he is still continuing to vomit. I'd try to get a ride with someone or take a bus if that is allowed in your area.
The lumps on his stomach could be benign but they could also be restricting something in his digestive track which is causing him to vomit. 4 days is a long time for this to continue. Dehydration is a major concern not to mention he has probably not been able to absorb any nutrients from his food because it is not staying in his stomach long enough.
Please try to get him to a vet someplace.
Good luck.